Polycystic ovary syndrome (PCOS) is a poorly undcrstood disorder which seems to be due to dysregulation of steroidogenesis, resulting in a high serum testosterone level. A promoter variant of 17beta-hydroxysteroid dehydrogenase type 5 (17beta-HSD5), a major determinant of ovarian testosterone formation, contributes to testosterone excess in PCOS. We propose to test the concept that 17beta-HSD5 activating variants interact with specific endocrine factors to determine ovarian testosterone secretion in both normal and PCOS patients in a clinical research project that will manipulate LH, insulin, and FSH levels. The specific aim is to test the hypothesis that the phenotype of an activating variant of the 17beta-HSD5 gene depends on interaction with LH, insulin resistant hyperinsulinemia, and FSH-dependent granulosa cell factors. The sub-aims are to ascertain the role of the variant genotype: 1) as a determinant of ovarian testosterone secretion in response to LH in normal and PCOS subjects, 2) as a determinant of ovarian testosterone secretion in response to insulin excess in PCOS, and 3) as a determinant of ovarian testosterone secretion in response to FSH-inducable ovarian factors. We will begin by determining the testosterone response to the LH analog human chorionic gonadotropin (hCG) in PCOS and control women of known 17beta-HSD5 genotype at the "A/G" promoter site. Then we will determine the effects of suppressing gonadotropins with a GnRH agonist, suppressing insulin with a thiazolidinedione (TZD), and stimulating granulosa cell function with FSH. The effects of the TZD on LH pulse characteristics and indexes of insulin secretion/sensitivity will also be assessed. The primary endpoint is the testosterone response to hCG, which will be related by analysis of variance to the 17beta-HSD5 genotype. If our hypothesis is correct, we expect LH, insulin, and inhibin B levels to be related to successively higher testosterone responses to hCG in subjects lacking, heterozygous, and homozygous for activating 17beta-HSD5 variants. If the data support the hypothesis, it would be the first direct evidence for a specific PCOS phenotype (ovarian testosterone secretion) resulting from interactions between a specific genetic trait (17beta-HSD5 variant) and the endocrine mileau (e.g., with respect to LH, insulin, and FSH levels).